Biodegradable polyester is a kind of macromolecule material using biological resources as raw materials. With respect to a petroleum-based polymer using petrochemical resources as raw materials, the biodegradable polyester can be degraded during a process of biological or biochemical effect or in a biological environment, being a very active degradable material in the present biodegradable plastic research and one of the best degradable materials in market application.
The biodegradable polyester, having characteristics such as soft texture, non-toxicity, being convenient to process, good chemical stability, a certain strength, very good chemical solvent resistance and cold resistance, is widely used in a field of agricultural mulching film. Owing to a special function of the agricultural mulching film, there is relatively high demand for transparency and special need for a UV resistance function. At present, a conventional method for enhancing the UV resistance function of a biodegradable polyester film is to add a certain amount of UV resistance additive, UV absorbent or UV stabilizer into the biodegradable polyester film. As in CN 103687902, UV absorbent and HALS stabilizer, or a light stabilizer combining both, is introduced and used for providing the mulching film with UV stability. However, an addition of UV resistance, UV absorbent or UV stabilizer will slow down a degradation rate of the biodegradable polyester film to some extent, resulting in that the biodegradable polyester film cannot finish degradation within an expected time, which affects renewing soil as well as cultivating crops and reduce fertility of soil to some extent.
The present invention surprisingly finds by research that by adding a trace amount of styrene into a formula of the biodegradable polyester composition, the biodegradable polyester composition is guaranteed to have excellent transmittance and haze effect, and meanwhile the biodegradable polyester composition is guaranteed to have suitable UV resistance function, without reducing the degradation rate of the biodegradable polyester composition.